2FA bypass flaw on cPanel threatens the security of 70 million domains

A vulnerability affecting the cPanel & WebHost Manager (WHM) web hosting platform could allow an attacker to bypass two-factor authentication (2FA) and conduct a brute force attack to infiltrate user accounts.

Such an attack can be accomplished in minutes, according to researchers with Digital Defense, enabling hackers to gain unwarranted access to users’ website management tools and compromise the sites they host on cPanel.

Hosting providers and users can utilise cPanel & WHM as a suite of tools for the Linux operating system to automate server management and web hosting tasks while simplifying the process of web hosting for the user. The platform claims to host more than 70 million domains in total launched on servers using cPanel & WHM.

“Our standard practice is to work in tandem with organizations on a coordinated disclosure effort to facilitate a prompt resolution to a vulnerability,” said Digital Defense senior vice president of engineering, Mike Cotton.

“The Digital Defense VRT reached out to cPanel who worked diligently on a patch. We will continue outreach to customers ensuring they are aware and able to take action to mitigate any potential risk introduced by the vulnerability.”

Although 2FA has been widely understood to be a useful added layer of protection above password security, the reliability of which many in the security industry have mixed feelings about, several bypass techniques have been devised lately.

One prominent example from earlier this year is an Android banking trojan that was able to bypass 2FA by compromising a device’s accessibility features. Also discovered in just September were critical vulnerabilities in multi-factor authentication (MFA) protocols based on the WS-Trust security standard. Exploiting this flaw could allow hackers to infiltrate core Microsoft services, such as Microsoft 365.

Last year, security researcher Piotr Duszynski even launched a tool that could bypass a number of 2FA schemes widely used across platforms such as Gmail and Yahoo.

According to an advisory issued by cPanel, the 2FA cPanel Security Policy didn’t prevent an attacker from repeatedly submitting 2FA codes. This allowed an attacker to bypass the 2FA check using brute force techniques. Essentially, an attacker could try limitless variations of 2FA codes until landing on the right one to access the account.

To fix the situation, incorrect 2FA codes are now treated as the equivalent of a failed password validation attempt. The issue has now been resolved in several builds including 11.92.0.2, 11.90.0.17 and 11.86.0.32.